Author: Flora Liu, MD
IARS and SOCCA 2026 Annual Meeting coverage
Electroencephalography allows anesthesiologists to monitor the brain—the primary target organ of general anesthesia. However, relying solely on a proprietary processed EEG number can overlook important information contained in the raw waveform, density spectral array, and spectral edge frequency.
At the 2026 IARS and SOCCA Annual Meeting, experts explained how anesthetic EEG patterns change dramatically from infancy through old age and why monitoring must be interpreted according to the patient’s developmental and functional brain status.
Matthias Kreuzer, PhD, emphasized that EEG may reflect a patient’s functional brain age more accurately than chronological age. Functional age incorporates brain structure, network connectivity, neurochemistry, cognitive health, and the brain’s response to anesthetic medications.
EEG characteristics change rapidly during the first two years of life. Infants younger than six months generally lack the organized alpha oscillations commonly seen in anesthetized adults. In those younger than three months, slow delta activity predominates, and conventional measurements such as the burst-suppression ratio may be unreliable.
Aging produces a different set of changes. Older patients typically have lower EEG amplitude and higher baseline frequencies, which can cause processed EEG monitors to display unexpectedly high index values despite adequate anesthesia.
Because many commercial algorithms do not sufficiently adjust for age, the same numerical target cannot safely be applied to neonates, adults, and elderly patients.
Evidence suggests that EEG-guided anesthetic titration intended to prevent burst suppression may reduce emergence delirium in children and postoperative delirium in older adults.
Carolina Frederico, MD, EDAIC, discussed EEG monitoring in elderly and critically ill patients. Baseline processed EEG values often increase with age. Attempting to lower the index to a predetermined target without examining the underlying EEG may lead to excessive anesthetic administration.
Age-related reductions in alpha power may reflect impaired thalamocortical connectivity and increased cortical vulnerability. As a result, older patients can enter burst suppression at relatively low anesthetic concentrations.
Intraoperative burst suppression has been associated with postoperative delirium. Dr. Frederico recommended gentle induction and careful titration to reduce unnecessary suppression of brain activity.
EEG may also reveal signs of inadequate analgesia or nociceptive stimulation, including:
- Beta arousal
- Loss of alpha activity
- Paradoxical delta arousal
- Abrupt changes in the density spectral array
Her recommended order of interpretation is straightforward: examine the raw waveform first, review the density spectral array second, and consider the processed index last.
Mauricio Ibacache, MD, PhD, reviewed EEG interpretation in neonates and infants. These patients may be particularly sensitive to anesthetics and vulnerable to hemodynamic instability and excessive drug exposure.
Neonates have immature corticothalamic and thalamocortical pathways, resulting in predominantly slow-delta activity. Between approximately three and nine months, alpha activity begins to appear but remains poorly organized. More adult-like alpha patterns generally emerge as the corpus callosum and related networks mature.
EEG discontinuity is common in premature infants but is considered abnormal in awake full-term neonates. It may also occur during infant anesthesia and could indicate excessive anesthetic exposure, although its complete clinical significance remains uncertain.
In infants younger than six months, combining the density spectral array with spectral edge frequency may provide more useful guidance than relying on a processed index.
For infants approximately three to six months old:
- Spectral edge frequency below 10 Hz may indicate deep anesthesia
- Values between 10 and 15 Hz may represent adequate anesthesia
- Values above 15 Hz may suggest light anesthesia or emergence
In neonates younger than one month, isoelectric periods visible on the density spectral array may indicate excessive anesthesia. Spectral edge frequency alone does not reliably correspond with anesthetic concentration in this age group.
Key Takeaways
Processed EEG indices should not be interpreted without examining the patient’s age, clinical condition, raw waveform, density spectral array, and spectral edge frequency.
The classic adult alpha-delta anesthetic pattern does not reliably appear during early infancy. Neonates and young infants require developmentally appropriate EEG interpretation.
Older adults often have reduced alpha power and an increased susceptibility to burst suppression. Chasing a predetermined processed EEG number may result in anesthetic overdose.
Avoiding unnecessary burst suppression may reduce postoperative delirium and improve neurologic recovery in vulnerable patients.
The most useful approach is to examine the raw EEG first, interpret the density spectral array and frequency distribution, and use the proprietary index only as supplementary information.
Understanding age-specific EEG patterns allows anesthesiologists to personalize drug dosing and provide more precise brain-directed care throughout the lifespan.
Thank you to IARS and SOCCA for allowing us to summarize this important coverage from the 2026 Annual Meeting.